Adjustable eccentric



Nov. 2, 1948. R. JOHNSON 2,453,072

ADJUSTABLE ECCENTRIC Filed April 24, 1947 4 Sheets-Sheet 1 INVENTOR. 1BY 134915 EJ571540? ATTORNEY Nov-{2, 1948. R. E. JOHNSON 2,453,072

' f N 1 x ADJUSTABLE ECCENTRIC. Filed A ril 24, 1947 4 sheets-Ema 2 Ymu" WAQL @M M E Q nun:

INVEN TOR.

Ralph fiJfinw/on Y A T70R11 Nov; 2, 1948. R. E. JOHNSON ADJUSTABLE Emmm4 SheetsSheet 3 Filed A ril 24, 1947 IN VEN TOR.

Will [55" Arm/2M0" Nov. 2, 1948- R. E. JOHNSC JN ADJUSTABLE; ECCENTRIC 4Sheets-Sheet 4 Filed April 24, 1947 I N VEN TOR.

E Jfindon A MIA/[SS ATTORNEY Patented Nov. 2, 1948 ADJUSTABLE ECCENTRICRalph E. Johnson, Rahway, N. J assignor to The Singer ManufacturingCompany, N. J., a corporation of New Jersey Elizabeth,

Application April 24, 1947, Serial No. 743,583

This invention relates tosewing machines, and

more particularly to an adjustable eccentric device adaptable foractuating the feed-dog of a sewing machine in its work-advancingmovements which must be variable in magnitude to produce stitches of anylength within a given range. Accordingly, the illustrated eccentricdevice is adjustable to produce eccentric motions of any magnitudewithin a limited range.

An eccentric motion is, by definition, that motion which is producedbyrotating a circular element about an axis whose center is not thegeometrical center ofthe circular element. To vary the magnitude ofeccentric motions it follows that it is necessary only to vary theradial or linear distance between the center of rotation and thegeometrical centerof the circular element. It is possible also to shiftthis center of rotation, otherwise called the point of eccentricity,angularly, i. e., circumferentially with respect to the geometricalcenter. This angular displacement of the point of eccentricity in thecase of, an eccentric which actuates the feed-dog of a sewing machine inits work-advancing movements, varies the timing of that movement withrespect to the other sewing machine elements. More specifically, angulardisplacement of the point of eccentricity causes the work-advancingmotion of the feed-do to begin and to end at diiferent times in thestitch-forming cycle. The radial displacement, on the other hand, variesthe linear distance between the center of rotation and the geometricalcenter, hence varying the magnitude of the work-advancing movement ofthe feed-dog.

The present invention involves an adjutable eccentric device in which.by means of a unitary adjustment, the point of eccentricity may beshifted both angularly and radially in preestablished ratios, therebyvarying simultaneously both the magnitude and timing of theworkadvancing movement of the feed-dog.

Also within the purview of this invention is an adjustable eccentric ofthe illustrated type in which the angular component of displacement ofthe point of eccentricity is entirelyeliminated.

The structure and operation. of arepresentative form of the inventionare described in the following specification referring to theaccompanying drawings in which-,

Fig. 1 is a vertical section taken through the lon axis of a sewingmachine in which the invention has been incorporated.

Fig. 2 is a bottom viewof the sewing machine. Fig. 3 is a left end viewof 'thebed portion of Claims. (01. 74-571 the machine, with thehroat-plate sectioned to expose the feed-dog.

Fig. {l is a vertical section taken substantially along the line fll ofFig. 1. i

Fig. 5 is an enlarged longitudinal sectional viewof an adjustableeccentric device embodying the present invention;

Fig. 6 is a section taken along the line 6-43 of Fig. 5, and shows infull line the eccentric in its maximum eccentricity setting, andinsuperirnposed broken lines, the minimum eccentricity setting.

Fig. 7 is an exploded perspective view showing the component parts ofthe adjustable eccentric unit.

Fig. 8 is an enlarged sectional View of the eccentric taken along theline 88 of Fig. 5.

Figs. 9, 10, 11 and 12 arediagrams showingthe relative angular positionsof the adjusting elements of the eccentric for four typical stitchlengthsettings in the available range.

Referring more specifically to the drawings, a

representative form of the invention is shown incorporated in a sewingmachine comprising a bed 20 from one end of which rises a hollowstandard 2| which carries an overhanging bracket-arm 22 terminating in ahollow head 23. Rotatably journaled in the bracket arm 22 is a main orarm shaft 2 one end of which. carries a combined belt and ba1ance-whee125, the other end of which carries a crank-disk 26. Pivotally secured tothe crank-disk 26 is a connectinglink 2! which drives a needle-bar 28carrying aneyepointed needle 29. Also actuated from the crankdisk 26 bymeans of a suitable linkage is a thread take-up arm 30, the free end ofwhich is provided with. a thread-eye 3| through which the sewing threadpasses in its travel from. the supply to the needle. A spring-depressedpresser-bar 32, carrying presser-foot33, is operatively supported in thehead 23 in a usual manner. Cooperating with theneedle in the formationof stitches is the loop-taker L, secured upon a shaft 35 and driven bythe main shaft 24 through a usual linkage. i 1

A feed-dog 3 cooperates with the presser-foot 33 to advance thematerial. The feed-dog is mounted on a feed-bar 36 (Fig. 3) which ispivotally supported at one of its ends by an up standing arm 3?, and atits other end by a sub stantially horizontal arm 38. The horizontal arm38 is secured to a rock-shaft 39 which is mounted in the bed 20 by meansof pintle bearings 40 and il. Adjacent the bearing All, the rock-shaftso is provided with an arm :12 which,

cylindrical element 56.

is pinned to the lower end of a pitman link 43, the upper end of whichembraces a fixed eccentric 44 secured to the rotary arm shaft 24 by aset screw 45 (Fig. During rotation of the shaft 24, the eccentric 44will actuate the pitman 43, thereby oscillating the rock-shaft 39 which,through the arm 38, will cause the feed-bar 36 to rise and-fall once foreach rotation of the shaft 24. This movement of the feed-bar is commonlydesignated as feed' lift motion.

Work advancing motion is imparted to the feed-bar 36 by means of theupright arm 37 which is secured to a rock-shaft 46 mounted in the bed 26by means of pintle bearings. 41. Adjacent the pintle bearings 41, therock-shaft 46 is provided 1 with an arm 48 which is pivotally connectedto the lower end of a pitman link 49, the upper end of which embraces anouter cylindrical element 59 of an adjustable eccentric device E.Rotation of the shaft 24 causes the eccentric device E to actuate thepitman 49 which, in :turn, oscillates the rock-shaft 46 which, throughthe upright arm 31, causes the feed-bar v36 to reciprocatein asubstantially horizontal plane. Operating in timed relation with thefeed-lift motion, this horizontal movement causes the feed-dog 34 totrace a substantially elliptical path. It is apparent that varying theeccentricity of the eccentric device E will vary the magnitude of thehorizontal movement of the feed-dog 34, thereby changing the stitchlength.

The adjustable eccentric device E comprises a driving disk or collar 56rigidly secured to the rotary arm shaft 24 by a set screw 5|. A channel52 in the driving disk 50 slidably receives a tongue portion 53 of anelliptical connecting link 54 which accommodates the rotary armshaft 2 4by means of an elongated slot 55 which limits the sliding movement ofthe elliptical connecting link 54 in the channel 52. A cylindricalelement 56 is rotatably mounted upon the shaft 24 by means of aneccentrically disposed aperture 51. An oil groove 58 is provided in thesurface of the cylinder 56 to conduct lubricant to the working elementsof the eccentric. outer cylindrical element 59 is provided with aneccentrically disposed aperture 66 by means of which it is rotatablymounted upon the inner A longitudinal slot 6| in the aperture 60 of thecylinder 59 provides an assembling clearance for a pivot-pin 62 which iscarried by the cylinder 56 and which protrudes beyond the peripherythereof. In its assembled position a portion of the pin 62 overhangs theface .63 of the cylinder 59. A slide-block 64 is provided with a hole 65by means of which it is mounted on the pin 52. In their assembledpositions, the pin 62, the slide-block 64 and a driving pin 66, which ismade integrally with the cylinder 59, all lie in the plane of theelliptical connecting link 54. This member is provided with slots 61 and68 which receive, respectively, the driving pin 66 and the slide-block64.

The'

made fast to the shaft 24 by the set screw 45. A spring 19 (Fig. 8)securedto the flange 69 by a screw 19', biases the slidablelocking-plate H so that its teeth 13 engage the teeth 14 of the disk i5.Two arcuate ribs 80, projecting from one face of the flange 69, serve asbearings to position the toothed -disk 75.. r-Fona'rmore completedisclosure of a similar construction including the flange 69, theslidable locking-plate H, and the toothed disk l5, reference may be hadto the U. S, patent of R. Kaier, No. 2,161,579.

To adjust the eccentric device: With the sewqing machine stopped, aspring retracted plunger- :pin: 81;.mo1intedrin the bracket-arm 22, ismanuallydepressed, and the shaft 24 rotated by hand by means ofthebalance-wheel until the plunger-pin 6| engages a slot 82 in one endof the slidable locking-plate 7!. Additional pressure on the plunger-pincauses the locking-plate H to slide against the action of the spring!51.9 1(Fig-i8), thereby disengaging. the locking-platea teeth 13 fromthe disk teeth 14 which frees the. inner Integral with the cylindricalelement 56 is .a

flange portion 69, formed with a channel 10 which receives a slidablelocking-plate H. This locking-plate is formed with a struck out portion12 which is provided with teeth 13 adapted to engage the peripheralteeth M of a disk 15 mounted The pin H is anchored inJthe cylindricalelement 56 from the shaft 24. When engaged by theplunger-pin 8|, thelocking-plate in is thereby locked to the frame of the sew ng machine.Consequently, the inner cylindrical element 56 :is effectively locked tothe frame of the machine since the locking-plate ll iscrecessed in thechannel 16 of the flange portion 69 ofthe inner: cylindrical element.'By maintaining the plunger-pin '6! .in its depressed position, theshaft '24 may 'be rotated a limited amount relatively to theinnerccylindrical element 56.

Relative rotation is also set up :between the shaft 24 and the outercylindrical element 59 by means of a motion-modifying driving connectiontherebetween. 'The' adjusting rotation of the shaft 24 is imparteddirectly to the ellipticalconnecting link 54 by means of the dri vingdisk 56 which a'ccommodates'the elliptical member in the channel 52.This rotation of the elliptical member is, in turn,'transmitted to theouter cylindrical element 59 through the driving pin 66. Inaddition toits angular rotation, the elliptical connecting link '54 slideslaterally in the channel 52. This sliding movement imparts additionalrotation to the cylindrical element 59 through the driving pin 66. Thesliding movement is caused by the fact that the ellipticalconnecting'link 54 is constrained by the slide-block 64 mounted on thepin 62 which is integral with the stationary, inner cylinder element 56.Because the'pin'62 is secured against rotation, the elliptical member54, when rotated by the driving-disk 5 6,is forced to pivot about'thepin 62. In order to pivot about the pin 62, which isspaced from thecenter of rotation of the shaft 24, the elliptical member mustnecessarily shift laterally inthe channel 52. Thus the outer cylindricalelement 59 is caused to rotate byan amount equal to the angular rotationof the shaft 25 plus that rotation *which-iscaused by the slidingmovement of the {elliptical connecting link 54.

It is to be understood from vthe foregoing description that duringadjustment of the eccentric device, relative angular motions are set upbetween: '(a) the actuating shaft 24 andthe inner cylindrical element56,, b) the inner cylindrical element 56 and the outer cylindricalelement :59, and .(c) the, outer cylindrical element 59' and theshaft24. Asa convenient means for indicating the amount ofadjustment ofthe eccentric, suitable calibrations are provided on. the inner face 83of the balance wheel 25 to cooperate with an indicating mark 84 on theframe ofthe sewing 1 machine (Fig- 1). t l i The mannersin which thecomponent elements of the eccentric unitlcooperate to establish theeccentricity is shown by Figs. 9-12. Fig; 9 shows the relative angularpositions of the elements at zero eccentricity. This setting correspondsto a stitch length of zero in which no work advancing motion is impartedto the feed-dog. Figs. 10 and 11 show the relative positions of theelements for providing approximately twenty-two and fourteen stitchesper inch, respectively. Fig. 12 showsthe relative positions for themaximum eccentricity attainable by the illustrated device, whichcorresponds to approximately five and onehalf stitches per inch in theillustrated machine.

Referring to the diagrams, it will be noted that letters are used toidentify geometrical points, as distinguished from numerals whichidentify mechanical elements. The letters is the geometrical center ofthe shaft 24, i is the geometrical center of the inner cylindricalelement 56, and 0 the geometrical centerof the outer cylindrical elementThe center of rotation of the shaft 24 is, of course, coincident withits geometrical center 5. The center of adjusting rotation of the innercylindrical element 56 (because it isrotatably mounted on the shaft 24)is the geometrical center s of that shaft. It follows that the outercylindrical element 59 (because it is rotatably mounted upon the innercylindrical element 56) has for its center of rotation the geometricalcenter i of the inner cylindrical element. It should be noted that thecenters of rotation z and 0 have significance only during adjustmcntofthe eccentric device, since thedriving operation of the eccentric isperformed with the three elements 24, 56 and 59 locked together to forma unitary structure whose center of rotation is the center 3 of theactuating shaft 24.

The eccentricity of a circular element is by definition the lineardistance between its center of rotation and its geometrical center. Thusthe distance 8-2, is thejeccentricity of the inner cylindrical element56, with respect to the shaft 24. The distance i-o is the eccentricityof the outer cylindrical element 59 with respect to the innercylindrical element 56. The vectorial sum of these distances is s,fo,which represents the resultant or total eccentricity of the adjustableeccentric unit. When the eccentricities s-i and i-o (which are equal inmagnitude in this unit) are opposed as in Fig. 9, the resultanteccentricity is zero and the center of rotation s and the geometricalcenter 0 are in coincidence. In Fig. 12, which is the maximum adjustmentfor the illustrated unit, the eccentricities s-z and z-o add vectoriallyto produce the resultant s -o.

If the line joining the center of rotation and the geometrical center ofeither cylindrical element be extended, the intersection of the linewith the periphery of the element will be the point farthest from thecenter of rotation. This point is termed the high-point. In Figs. 9- 12,h represents the high-point of the outer cylindrical element 59, hi thehigh-point of the inner cylindrical element 56, and H the resultanthighpoint of the two combined eccentricities, found by extending theresultant line so.

In Fig. 9 the distance s-o is zero, therefor no high-point H exists. InFig. 10 the shaft 24 has been rotated counterclockwise twenty-:twodegrees. This amount of shaftjrotation, because the latter to rotate inthe same direction for thirty-eight degrees. The high-point H, whichbegan its generation at the point b, has been rotated sixteen degrees inthe direction of rotation of the shaft. The relative motion, or netangular displacement, between the shaft 24 and the high-point H is;therefore, six degrees. This angular displacementrepresents a change inthe timing of the work-advancing component of the feed-dog motion forthe reason that all of the sewing machine mechanism, except that which iis concerned with the work-advancing movement of the feed-dog, has beendisplaced inproportion to the twenty-two degrees of rotation of the armshaft 24, while the feed-dog has been displaced inproportion to thesixteen degrees of rotation of the high point H.

of the action of the previously described motionmodifying drivingconnection between the shaft In Fig. 11 the'shaft 24 has been rotated conterclockwise thirty-two degrees from the position illustrated in Fig.9, which through the motionmodifying means has caused forty-eightdegrees rotation of the outer cylindrical element 59. The p high-point Hhasbeen rotated twenty-threadegrees, leaving a net angular displacementof nine degrees between the point H and the shaft 24.

In Fig. 12 the shaft has been rotated counterclockwise ninety-threedegrees, thereby causing one hundred and fifty degrees rotation of theouter element 59, the result of which is seventyfive degrees of rotationof the high-point H. The

difference between the angular rotation of the shaft 24 and thehigh-point His eighteen degrees which is the maximum relativedisplacement provided by theillustrated eccentric device.

The angular rotations of each of the three adjusting elements includingthe shaft 24, the inner cylindrical element, 56, and the outercylindrical element. 59, are shown in the diagrams to :be

measured with respect to a fixed point, such as i the frame of thesewing machine. It should be noted, however, that adjustment of theeccentric device dependsupon the relative rotation of each of the threeelements with respect to the other two; Thus it is possible to adjustthis eccentric device With identical results by holding stationary theshaft 24 and rotatingthe inner cylindrical element 56 by means of itsflange portion .69.. The absolute angular rotations, i. e. rotationswith respectto a fixed point, will be changed, but the relativerotationsbetween the three elements as well as the displacemen'tof the high-pointH with respect to the shaft 24 will be unchanged. Likewise similaradjustin results could be obtained by holdingstationary the outercylindricalelement 59 and setting up relative adjusting rotation betweenthe shaft24 and the inner cylindricalele ment 56.. This Wouldinvolve thesimple structural modification. of interchanging the distance betweenthepin 65 and the center of the shaft 24 with the distance between thepin 52 and the cylindrical. element. 59 will result in limited relativemovement between the outer cylindrical ele ment 59 andthe-shaft 24. Thismotion is caused bythe'fixe'deccentricity of theinner cylindricalaircrew element .56 with respect toithev'shaft:andicannot beeliminated.The effectrisrillustratedibysEignll of the U. S. patent of A. Grieb, No.1,605,937. The instant invention, however,isdistinguishable in that itconcerns relative movement between the shaft 26- and the outercylindrical element 59 in addition to that causediby'thefixedeccentricity of the inner cylindrical element '56 .with"respect tothe shaft.

justingmechanism for said eccentric; unit comprising motion-modifyingdriving linkage operatively associatedwith said cylindrical elements.

2. 'In a sewing machine having a frame, a shaft rotatably mounted insaid frame,.and mechanism adapted to beactuated by said shaft; aneccentric unit mounted upon said shaft comprising an inner cylindricalelement eccentricall apertured and thereby rotatably mounted upon thesaid. shaft, an outer cylindrical element eccentrically apertured androtatably mounted thereby upon the said inner cylindrical element, andunitary means for adjusting said eccentric unit, comprisingmotion-modifying driving connections for effecting relative angularrotation between said shaft, inne cylindrical element, and outercylindrical element in which the outer cylindrical element is rotatedrelatively to the inner cylindrical element, the inner cylindricalelement is rotatedrelatively to the actuating shaft, and the shaft isrotated relativel to the outer cylindrical element by an r amountexceeding that which is caused by the fixed eccentricity of the saidinner cylindrical element with respect to the actuatingshaft.

3. In a sewing machine having a frame, an actuating shaft rotatablymounted in said frame, and mechanism adapted to be actuated by saidshaft; an adjustable eccentric unit mounted on said actuating shaft andcomprising, a rotatable inner cylindrical element eccentricallyvapertured to accommodate said actuating shaft, a rotatable outercylindrical element eccentric'ally apertured to accommodate said innercylindrical element, and unitary adjusting means comprisingmotionmodifying drivin connections for effecting relative angularrotation between the said shaft, inner cylindrical element, and outercylindrical element, in which the shaft is rotated an absolute angulardistance exceeding that of...the inner cylindrical element, and theouter cylindrical element is rotated an absolute angular.distanceexceeding that of the shaft plus that rotation of the outercylindrical element which is caused by, the fixed eccentricity of the.inner cylindrical element with respect to the shaft.

4. In a sewing machine having a frame; a shaft rotatably mounted in saidframe, and mechanism adapted to be actuated by .said shaft; anadjustable eccentric unit mounted upon said shaft, comprising an innercylindrical element eccentrically apertured to accommodate the saidshaft, ,an outer cylindrical element eccentrically apertured toaccommodate said innerv cylindrical element, and adjusting mechanism forsaid eccentric unit comprising a motion-modifying driving connectionbetween the said shaft and theoutercylin- 8 meals-element 101":establishing rotatiozr dhereba. tween by an amount differing.fronrithatzcaused byztheifixed eccentricity of the :innerrcyiindiicalelement with respect :to: thewshaft.

.lnasewin imachine having a, frame, ashaft rotatably; mounted in .'-said:frame; and mechanism adaptedito-be actuated l y-said shaft; ranadjustable eccentric unit -c om prising-an innericylindri'cal elementeccentrically 'aperturecl and rotatably mounted thereby-31min said.shaftgan eouter -;cylindrical. element eocentrieally :apertured androtatably mounted thereby-upon the saidinner cylindr-i'cal element, :andunitaryadlusting mechanism, for :said eccentric. comprising -.amotionmodifying driving connection between the-said shaft and the saidinner cylindrical; element.

.6 In .a sewing machine havingia frame,;.;an actuating shaft-rotatably:mounted in said frame, and mechanism adapted to betactuated by. saidShaft}. an eccentric unit mounted upon saidshaft and comprisingzan innercylindrical element -60? centrically apertured .and thereby. rotatablymounted upon said shaft, an outer cylindrical element .eccentricallyapertured and rotatably mounted thereby upon the said inner cylindricalelement, andv unitary adjusting, means for said eccentric unitcomprising; a motion-modifying driving connection betweensaid inner andouter cylindrical elements.

7. ..In asewingmachine having aframe, ashaft rotatablymountedin saidframe, and mechanism adapted ,tobe actuated by said shaft; an adjustableeccentric unit mounted. uponsaiol shaft, said. eccentric .unitcomprising aninner cylindrical elei .menteccentrically apertured toaccommodate .the

said, shaft, an outer cylindrical element ieccentrically apertured toaccommodate said inner cylindrical .element, releasable means forlocking .oneof said cylindrical elements to said frame, and aunitaryrmeans for adjusting saideccentric unit comprising amotion-modifying driving connection between the other of saidcylindrical elements and the, said shaft.

' 8. In asewing machine having a frame, a shaft rotatably mounted insaid frame, and mechanism adapted to be actuated by said shaft; anadjustableeccentric unit comprising an inner cylindrical elementeccentrically. apertured and rotatably mounted thereby upon said shaft,an outer cylindrical element eccentrically aperturedand rotatably.mounted thereby upon the ,said inner'cylindrical element, a collarmounted upon said shaft, a pin eccentricallydisposed with respect to thesaid shaft, a connecting, link slidably mounted in said collar andpivotally constrained by said pin, and an operative driving connectionbetween said link and said outer cylindrical element.

' 9. In a sewing machine having. aframe, a shaft rotatably mounted insaidjframe, and mechanism adapted tojhe actuatedby said shaft; anadjustable eccentric unit comprising an inner cylindrical elementeccentrically apertured parallel to its center-line and rotatably,mounted thereby upon the..sa id..shaft,,an outer cylindrical. elementeccentrically apertured parallel to its center-line androtatably mountedthereby upon said inner cylindrical element, a collar mounted upon saidshaft, a pin eccentricallydisposed with respectto the center ofsa'idshaft, aconnecting link slid ably mounted in said. collar andpivotally constrained by, saidpin, ,and an operative driving connectionbetween said link and said inner cylindrical element.

ML- Ina sewing machine having a frame, a shaft rotatably mounted in saidframe, and. mechanism adapted to be operated by said shaft; an adjust-REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Number Date 1,605,937 Grieb Nov. 9, 19261,956,447 Laessker Apr. 24, 1934 10 2,161,579 Kaier June 6, 1939 ZonisJan. 20, 1942

